use std::path::{Component, Path, PathBuf};

pub fn is_cur_dir<P: AsRef<Path>>(path: P) -> bool {
    path.as_ref()
        .components()
        .next()
        .map_or(false, |c| c == Component::CurDir)
}

/// ```
/// # use std::path::{PathBuf};
/// # use erg_common::pathutil::add_postfix_foreach;
/// let path = PathBuf::from("erg");
/// let path = add_postfix_foreach(path, ".d");
/// assert_eq!(path, PathBuf::from("erg.d"));
/// let path = PathBuf::from("erg/foo/bar");
/// let path = add_postfix_foreach(path, ".d");
/// assert_eq!(path, PathBuf::from("erg.d/foo.d/bar.d"));
/// ```
pub fn add_postfix_foreach<P: AsRef<Path>, Q: AsRef<Path>>(path: P, postfix: Q) -> PathBuf {
    let mut result = PathBuf::new();
    for c in path.as_ref().components() {
        match c {
            Component::Prefix(_) => result.push(c),
            Component::RootDir => result.push(c),
            Component::CurDir => result.push(c),
            Component::ParentDir => result.push(c),
            Component::Normal(os_str) => {
                let mut os_string = os_str.to_os_string();
                os_string.push(postfix.as_ref().as_os_str());
                result.push(PathBuf::from(os_string));
            }
        }
    }
    result
}

pub fn remove_postfix_foreach<P: AsRef<Path>>(path: P, extension: &str) -> PathBuf {
    let mut result = PathBuf::new();
    for c in path.as_ref().components() {
        match c {
            Component::Prefix(_) => result.push(c),
            Component::RootDir => result.push(c),
            Component::CurDir => result.push(c),
            Component::ParentDir => result.push(c),
            Component::Normal(os_str) => {
                let string = os_str.to_string_lossy();
                result.push(string.trim_end_matches(extension));
            }
        }
    }
    result
}

/// cutout the extension from the path, and let file name be the directory name.
/// ```
/// # use std::path::{PathBuf};
/// # use erg_common::pathutil::remove_postfix;
/// let path = PathBuf::from("erg.d.er");
/// let path = remove_postfix(path, ".er");
/// assert_eq!(path, PathBuf::from("erg.d"));
pub fn remove_postfix<P: AsRef<Path>>(path: P, extension: &str) -> PathBuf {
    let string = path.as_ref().to_string_lossy();
    PathBuf::from(string.trim_end_matches(extension))
}

///
/// ```
/// # use std::path::{PathBuf};
/// # use erg_common::pathutil::squash;
/// let path = PathBuf::from("erg/../foo");
/// let path = squash(path);
/// assert_eq!(path, PathBuf::from("foo"));
/// let path = PathBuf::from("erg/./foo");
/// let path = squash(path);
/// assert_eq!(path, PathBuf::from("erg/foo"));
/// ```
pub fn squash(path: PathBuf) -> PathBuf {
    let mut result = PathBuf::new();
    for c in path.components() {
        match c {
            Component::Prefix(_) => result.push(c),
            Component::RootDir => result.push(c),
            Component::CurDir => {}
            Component::ParentDir => {
                result.pop();
            }
            Component::Normal(os_str) => {
                result.push(os_str);
            }
        }
    }
    result
}